It really depends on the brand, and popular brands aren’t necessarily the healthier brands. We use Taste of the Wild with our dogs, which our vet approves of. It’s not like that. This is the variety we usually get them:
It used to be, though from the 80s or so onwards, pet food companies started doing research into the nutritional needs of household animals and making food that was formulated more precisely than “whatever was on the abattoir floor”. They now have breed-specific dog foods and foods for cats with kidney issues and so on.